Field of the Invention
The present invention generally relates to mobile communications technologies, and more particularly, to Channel State Information (CSI) feedback.
Description of the Prior Art
In a modern mobile communication system such as a Long Term Evolution (LTE) system, a base station determines a transmission format, a transmission block size, a modulation and coding scheme, a Multiple Input Multiple Output (MIMO) transmission mode and the like to be used in a downlink (DL) and an uplink (UL). To perform such determination for the DL, the base station needs information about the performance of a current DL channel from a User Equipment (UE), and the information is generally referred to as Channel State Information (CSI).
Frequency Division Multiplexing (FDD) DL coordinated multi-point (coordinated multi-point, CoMP) transmission has potential in improving the coverage area, cell edge throughput, and/or spectral efficiency. In the CoMP transmission, multiple transmission modes exist, such as Joint Transmission (JT), Dynamic Point Selection (DPS), Dynamic Point Blanking (DPB), and Coordinated Scheduling/Beamforming (CS/CB). Moreover, the DPS may be combined with the JT. In addition, a hybrid type of the JT and the CS/CB is also possible.
The diversity of the transmission mode in the CoMP means that the UE may be faced with multiple interference assumptions, so interference measurement for the CoMP is necessary. Because of the introduction of an Interference Measurement Resource (IMR), a conventional CSI report mode is no longer applicable.